The Echinoid Directory

Stylocidaris Mortensen, 1909, p. 52

[=Hesperocidaris Mortensen, 1928, p. 73, type species Dorocidaris panamensis Agassiz, 1898]

Diagnostic Features
  • Test moderately thick.
  • Apical disc about 50% of test diameter; generally monocyclic with oculars narrowly insert. Genital plates all similar in size; apical disc plates uniformly covered in tubercles.
  • Interambulacra with 6-8 plates in a series. Primary tubercle perforate, non-crenulate or weakly subcrenulate adapically; areoles circular and incised; widely separated.
  • Scrobicular tubercles not much differentiated. Extrascrobicular zones small and densely covered in heterogeneous secondary tubercles and granules.
  • Interradial and perradial sutures weakly incised.
  • Ambulacral zones weakly sinuous. Pore- zones a little incised; pore-pairs non-conjugate. Perradial zone with marginal series of contiguous primary tubercles plus much smaller inner series.
  • Peristome smaller than apical disc. Ambulacral plates uniserial in each column; interambulacral series reaching the mouth.
  • Primary spines weakly fusiform and slender; neck and collar short; shaft ornamented by beaded or serrated ribs.
Miocene to Recent, widespread.
Name gender feminine
Cidaris affinis Philippi, 1845, p. 351, by original designation.
Species Included
  • S. affinis (Philippi, 1845); Recent, Mediterranean, Atlantic, Caribbean.
  • S. lineata Mortensen, 1910; Recent, Caribbean.
  • S. reini (Doderlein, 1887); Recent, Indo-West Pacific.
  • S. amboinae Mortensen; Recent, Indo-West Pacific.
  • S. annulosa Mortensen, 1927; Recent, Philippines.
  • S. conferta (Clark, 1916); Recent, Australia.
  • S. rufa Mortensen, 1928; Recent, Hawaii.
  • S. calacantha (Agassiz & Clark, 1907); Recent, Hawaii.
  • S. bracteata (Agassiz, 1879); Recent, Indo-West Pacific.
  • S. maculosa Mortensen, 1928; Recent, North West Pacific.
  • S. effluens Mortensen, 1927; Recent, Philippines.
  • S. tiara (Anderson, 1894); Recent, Indian Ocean.
  • S. lorioli (Koehler, 1927); Recent, Indian Ocean.
  • S. albidens Clark, 1925; Recent, Indian Ocean.
  • S. badia Clark, 1925; Recent, Mauritius.
  • S. brevicollis (de Meijere, 1904); Recent, Indo-West Pacific.
  • S. fusispina Mortensen, 1928; Recent, Japan.
  • S. melitensis (Wright, 1855); Miocene, Mediterranean.
Classification and/or Status

Cidaroida, Cidaridae, Cidarinae.

Possibly not a monophyletic group. Treated here as a subgenus of Tretocidaris.


Distinguished from Tretocidaris by having no end tooth to its globiferous pedicellariae. In its test morphology there is little to distinguish the two. I here follow Clark (1909) who placed Cidaris affinis in the genus Tretocidaris on the basis of test characteristics.

Clark, H. L. 1909. The Cidaridae. Bulletin of the Museum of Comparative Zoology at Harvard College 51(7), 165-230, pls 1-11.

Mortensen, T. 1928. A monograph of the Echinoidea. 1, Cidaroidea. C. A. Reitzel, Copenhagen.